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    <title>Document</title>
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        window.onload=function(){
            //1.获取画布
            var canvas=document.getElementById('canvas');
            //2.获取上下文对象
            var cx=canvas.getContext('2d');
           function clock(){
                //3.设置画笔样式
                cx.fillStyle='green';
                cx.strokeStyle='black';
                //4.绘制图形
                    //绘制表盘
                    cx.beginPath();
                    cx.arc(300,300,200,0,Math.PI*2);
                    cx.closePath();
                    cx.fill();
                    //绘制时刻度
                    cx.strokeStyle='black';
                    cx.lineWidth=2;
                    for(var i=0;i<12;i++){
                        cx.save();
                        cx.translate(300,300);
                        cx.rotate(i*(Math.PI/6));
                        cx.beginPath();
                        cx.moveTo(0,-180);
                        cx.lineTo(0,-200);
                        cx.closePath();
                        cx.stroke();
                        cx.fillStyle='black';
                        cx.font='16px blod';
                        cx.rotate(Math.PI/6)
                        cx.fillText(i+1,-5,-220);

                        cx.restore();
                    }
                    //绘制分刻度
                    cx.lineWidth=2;
                    cx.strokeStyle='black';
                    for(var i=0;i<60;i++){
                        cx.save();
                        cx.translate(300,300);
                        cx.rotate(i*(Math.PI/30));
                        cx.beginPath();
                        cx.moveTo(0,-190);
                        cx.lineTo(0,-200);
                        cx.closePath();
                        cx.stroke();
                        cx.restore();
                    }
                    //获取当前时间
                    var today=new Date();
                    var hour=today.getHours();
                    var min=today.getMinutes();
                    var sec=today.getSeconds();
                    hour=hour+min/60;
                    //绘制时针
                    cx.save();
                    cx.translate(300,300);
                    cx.rotate(hour*Math.PI/6);
                    cx.beginPath();
                    cx.moveTo(0,10);
                    cx.lineTo(0,-120);
                    cx.closePath();
                    cx.stroke();
                    cx.restore();
                    //绘制分针
                    cx.save();
                    cx.translate(300,300);
                    cx.rotate(min*Math.PI/30);
                    cx.beginPath();
                    cx.moveTo(0,10);
                    cx.lineTo(0,-160);
                    cx.closePath();
                    cx.stroke();
                    cx.restore();
                    //绘制秒针
                    cx.lineWidth=1;
                    cx.strokeStyle='red';
                    cx.save();
                    cx.translate(300,300);
                    cx.rotate(sec*Math.PI/30);
                    cx.beginPath();
                    cx.moveTo(0,10);
                    cx.lineTo(0,-175);
                    cx.closePath();
                    cx.stroke();
                    cx.restore();
                    //绘制交叉处
                    cx.fillStyle='#ccc';
                    cx.strokeStyle='red';
                    cx.beginPath();
                    cx.arc(300,300,5,0,Math.PI*2);
                    cx.closePath();
                    cx.fill();
                    cx.stroke();
               setTimeout(clock,1000);
           }
           clock();
        }   
    </script>
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<body>
    <canvas id="canvas" width="600px" height="600px" style="background:#ccc"></canvas>
</body>
</html>